A semiconductor chip currently used is operated by an external battery or AC power source. Even though there is a unit, in the semiconductor chip, which operates from an external power source, all necessary power for the semiconductor chip is entirely dependent on an external power source, and there is no self-supplied power source in the chip. If a self-supplied power source is available, it is usually used as a standard power source for both memory and non-memory semiconductor chips, a backup power source, and a standby power source. In particular, an active RFID, SOC (system on a chip)), LOC (lab. on a chip), solar battery, and so on make best use of the self-supplied power source. For now, only the concept of a thin film battery and its possible application as a power source for a semiconductor chip has been established, and there has not been any report on an internal power source of the semiconductor chip. Therefore, a need exists to develop a concept and system for embedding an electric power supply into a semiconductor chip, and especially to establish its fabrication process simple and easy to operate.
In case of a conventional semiconductor device, transistors, resistors, and capacitors are all built on the front side of a silicon wafer, leaving no specific function for its back side except for the use as a supporter.
An existing fabrication method of a thin-film battery involves patterning a battery area while the semiconductor process is under way, followed by deposition and etching. Unfortunately, the method is exposed to an increase of fabrication cost related to photo lithography and to a change in properties of semiconductor wafers due to heat budget from a battery material subjected to high-temperature heat treatment.